Simple, cheap, effective auction site required like many of the eBay clones available at present for use on a Linux server with MySQL, PostgreSQL, cron available.
Categories and Sub-Categories, Searchable, PayPal integration, email between buyer/seller accounts, "Buy It Now" features, etc.
Classifieds and AutoBid function for buyers would be nice.
There will likely be extensive follow-up work for winning bidder once site is "off the ground".
Something you've already written is fine.. there are many posted here and at other freelancing sites.
Demonstration necessary.
Links of interest:
[login to view URL]
[login to view URL]
[login to view URL]